The present invention relates to a receiver for use in antenna switching diversity systems.
In radio communication, there is experienced a phenomenon known as fading, wherein electric field strength of received signals (referred to "field strength") is varied by the influence of radio wave reflections by buildings and hills, sometimes so intensely that wave reception is made totally impossible. One of the known techniques to cope with fading is called diversity reception, in which two antennas are provided so that reception can be achieved with one of them even if impossible with the other. Switching diversity systems, whose structure is simpler because only the antenna has to be duplicated but the receiver circuit does not, are especially effective for mobile communications, where equipment has to be particularly small. A prior art example of the switching diversity system is described in detail in Microwave Mobile Communications, 1974, John Wiley & Sons, pp. 399-401. The system described in the publication, however, involves the problem that antenna switching does not take place when the field strengths for both antennas become lower than the threshold.